Time-warping adjustment based on depth information in a virtual/augmented reality system

ABSTRACT

A technique includes determining a depth value for each of a plurality of pixels of a frame, down-sampling the depth values of a tile of the frame to obtain a plurality of down-sampled depth values, the frame including one or more tiles, determining a change in a head pose, determining, from the plurality of down-sampled depth values, a down-sampled depth value for a vertex, determining an adjusted position for the vertex based on the change in head pose and the down-sampled depth value for the vertex, performing, based on at least the adjusted position for the vertex, a depth-adjusted time-warping of the frame to obtain a depth-adjusted time-warped frame, and triggering display of the depth-adjusted time-warped frame.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, U.S.application Ser. No. 15/606,569, filed on May 26, 2017, which claimspriority to U.S. Provisional Application No. 62/342,999, filed on May29, 2016, and claims priority to U.S. Provisional Application No.62/354,443, filed on Jun. 24, 2016, the disclosures of which areincorporated herein by reference in their entireties.

FIELD

This document relates, generally, to a virtual or augmented realitysystem.

BACKGROUND

Performing video rendering can consume a significant amount of time andcomputing resources in a virtual reality (VR) environment. Videorendering may include, for example, a process by which a computerprocesses information from a coded data source and uses that informationto produce and display an image or series of images. A virtual realityapplication may receive or generate application data. A graphics orrendering engine may then render a frame to be displayed as part of thevirtual reality content. In some cases, while the graphics engine isrendering graphics for a frame, a user's head or VR headset (or headmounted display) may move, causing the location/orientation informationfor the user's head to be inaccurate by the time the frame is output tothe display.

SUMMARY

In one aspect, a method, may include determining a depth value for eachof a plurality of pixels of a frame, down-sampling the depth values of atile of the frame to obtain a plurality of down-sampled depth values,the frame including one or more tiles, determining a change in a headpose, determining, from the plurality of down-sampled depth values, adown-sampled depth value for a vertex, determining an adjusted positionfor the vertex based on the change in head pose and the down-sampleddepth value for the vertex, performing, based on at least the adjustedposition for the vertex, a depth-adjusted time-warping of the frame toobtain a depth-adjusted time-warped frame, and triggering display of thedepth-adjusted time-warped frame.

An apparatus may include at least one processor and at least one memoryincluding computer instructions, when executed by the at least oneprocessor, cause the apparatus to: determine a depth value for each of aplurality of pixels of a frame, down-sample the depth values of a tileof the frame to obtain a plurality of down-sampled depth values, theframe including one or more tiles, determine a change in a head pose,determining, from the plurality of down-sampled depth values, adown-sampled depth value for a vertex, determine an adjusted positionfor the vertex based on the change in head pose and the down-sampleddepth value for the vertex, perform, based on at least the adjustedposition for the vertex, a depth-adjusted time-warping of the frame toobtain a depth-adjusted time-warped frame, and trigger display of thedepth-adjusted time-warped frame.

A computer program product may include a non-transitorycomputer-readable storage medium and storing executable code that, whenexecuted by at least one data processing apparatus, is configured tocause the at least one data processing apparatus to perform a methodincluding: determining a depth value for each of a plurality of pixelsof a frame, down-sampling the depth values of a tile of the frame toobtain a plurality of down-sampled depth values, the frame including oneor more tiles, determining a change in a head pose, determining, fromthe plurality of down-sampled depth values, a down-sampled depth valuefor a vertex, determining an adjusted position for the vertex based onthe change in head pose and the down-sampled depth value for the vertex,performing, based on at least the adjusted position for the vertex, adepth-adjusted time-warping of the frame to obtain a depth-adjustedtime-warped frame, and triggering display of the depth-adjustedtime-warped frame.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example embodiment of a virtual reality system.

FIGS. 2A and 2B are perspective views of a head mounted display device,in accordance with an embodiment broadly described herein.

FIG. 3 is a block diagram of a virtual reality system, in accordancewith an embodiment broadly described herein.

FIG. 4 is a block diagram illustrating a virtual reality (VR) systemaccording to an example embodiment.

FIG. 5 is a diagram illustrating a frame vertex grid according to anexample embodiment.

FIG. 6 is a diagram illustrating pixel depth values for a frame or tileaccording to an example embodiment.

FIG. 7 is a diagram illustrating a down-sampling of pixel depth valuesto obtain a subset of down-sampled depth values for a tile or frameaccording to an example embodiment.

FIG. 8 is a diagram illustrating a frame vertex grid according to anexample embodiment.

FIG. 9 is a flow chart illustrating operation of a virtual realitysystem according to an example embodiment.

FIG. 10 illustrates an example of a computer device and a mobilecomputer device that can be used to implement the techniques describedhere.

DETAILED DESCRIPTION

According to an illustrative example embodiment, virtual reality, whichmay also be referred to as immersive multimedia or computer-simulatedlife, may, at least in some cases, replicate or simulate, to varyingdegrees, an environment or physical presence in places in the real worldor imagined worlds or environments. A Virtual Reality (VR) system and/oran Augmented Reality (AR) system may include, for example, ahead-mounted audio visual device, such as, for example, a VR headset, ahead mounted display (HMD) device, or similar device worn by a user, forexample, on a head of the user, to generate an immersive virtual worldenvironment to be experienced by the user. For example, a VR/AR systemmay generate a three-dimensional (3D) immersive virtual environment. Auser may experience this 3D immersive virtual environment throughinteraction with various electronic devices.

A sensing system may track the pose of the VR headset or user's head.Pose, may include, for example, position (or location) and/ororientation information for any object (physical or virtual), such as aVR controller (as an example). Pose may include, for example, absoluteor relative position, location and/or orientation of an object within aphysical world or of an object (e.g., virtual object or renderedelement) within a virtual world. A graphics engine (or graphicsprocessing unit (GPU)) may be used to render graphics of the VR contentfor display based on a current pose of the VR headset or user's head. Insome cases, while the graphics engine is rendering a frame, a user'shead or VR headset may move, causing the location/orientationinformation for the user's head pose to be inaccurate by the time theframe is output to the display.

According to an example embodiment, time-warping may be used to warp(e.g., shift, rotate, adjust or reproject) an image or frame to correctfor head motion or translation (change in the user's head pose) thatoccurred after (or while) the frame (or texture or image) was renderedand thereby reduce perceived latency. For example, a homograph warp mayuse homography transformation of the image to rotate the image based onpost-rendering pose information. Time-warp may include a synchronoustime-warp or an asynchronous time-warp. Also, time-warping may includerotational time-warping to adjust or shift an image due to rotation of auser's head, and positional time-warping to shift or adjust an image dueto translation (or change in position or location) of the user's head.Thus, according to an example embodiment, time-warp may include arotational time-warp component and a positional time-warp component dueto change in position or location of a user/user's head. According toexample implementation, time-warping, which may also be referred to asasynchronous reprojection or image warping, may include receiving animage that includes a 3D scene that has been projected to a plane, andthen reprojecting the 3D scene, where the reprojection is the 2D imagethat has been modified (e.g., shifted, rotated, or other modification)based on the user's updated head pose or change in head pose.

Also, according to an example implementation, time-warping (which mayalso be referred to as image warping or reprojection) may be consideredan image-based technique that generates new views from reference imagesby performing a per-pixel reprojection. In this way, the applicationframes can be transformed and re-projected for new object poses andcamera viewpoints. See, e.g., Smit, F. A., et al., 2010, AShared-Scene-Graph Image-Warping Architecture for VR: Low Latency VersusImage Quality, Computers & Graphics 34, Issue 1, Pages 3-16.

According to one or more example implementations, the technologiesdisclosed herein enable an improvement in user experience by, e.g.,performing a depth-adjusted time-warping of an image to reduce perceivedlatency without overburdening hardware or system resources (e.g.,without overburdening memory bandwidth, processor resources, and thelike).

According to an example embodiment, in order to improve the 3Dexperience of a VR system, the amount of time-warping applied to animage (or portions thereof) may adjusted or scaled based on a depth ofthe image. For example, as a user turns his head or changes his/herlocation, objects in a frame that are closer to the user should shift ormove more than objects that are farther away. According to an exampleembodiment, both a color value (e.g., indicating RGB/red green blue andalpha information for each pixel) and a depth value (e.g., indicating adepth or relative depth for a pixel) may be provided for each pixel ofan image. Thus, according to an example embodiment, a per-pixeltime-warping for a frame may be adjusted or scaled based on the depthvalue for each of the pixels of the frame.

According to an example embodiment, the color values and depth valuesfor a frame may be initially stored in a local memory (or GPU memory)for processing by the GPU/graphics engine. At least in some systems, inorder to perform time-warping on the frame, the color and depthinformation may be written from local (GPU) memory to main memory sothat time-warping on the frame may be performed by anotherprocessor/process or controller. However, there is typically a verylimited bandwidth between the local memory (e.g., GPU memory) and themain memory. Therefore, writing a large number of depth values for aframe out to a main memory for time-warp processing may add significantdelay to the processing/rendering of a frame. Also, the amount of timeto adjust or scale the time-warping for each pixel based on per-pixeldepth values may typically significantly increase the amount of time orlatency to perform the time-warping on the frame. Therefore, at least insome cases, due to such memory bandwidth constraints and/or processinglimitations of many VR systems or HMDs, it may be impractical or atleast technically challenging to adjust time-warping for each pixel of aframe based on depth values for each individual pixel of the frame.Alternatively, a single depth value may be used for the frame, and thenthe time-warping of the frame may be adjusted based on this single depthvalue for the frame. However, using a single depth value for a frame mayover-simplify the depth of the frame, and thus, for example, may notsufficiently accommodate or reflect the depth of various objects in aframe when performing time-warping for the frame.

Therefore, according to an example embodiment, a graphics engine or GPUprovided as part of a head mounted display (HMD) 100 (or as part of afirst electronic device 300), for example, may determine a subset ofdepth values for a frame, where the subset of depth values may be, forexample, greater than 1 depth value per frame, and less than a depthvalue for each (or all) pixels of a frame. Tile-based processing ofdepth values may be used to down-sample depth values of the tile toobtain a subset of down-sampled depth values, e.g., for each tile, wherethere may be one or more tiles per frame. In some cases, a full set ofdepth values for all pixels of a frame may be too large to be processedand down-sampled by a graphics engine/GPU. Hence, the graphicsengine/GPU may perform down-sampling of depth values for each tile of aframe. Once a set of down-sampled depth values have been determined foreach tile, these down-sampled depth values may be output from GPU/localmemory to main memory, so that these subset of down-sampled depth valuesmay be read or used by an electronic display stabilization (EDS) engineto perform depth-adjusted time-warping of the frame. By using a subsetof depth values from a frame, time-warping of the frame may be improvedfor a VR system, e.g., while not introducing significant delay to thetime-warp processing.

According to an example embodiment, a frame may include or may bedivided into a plurality of tiles (or sections), and a depth value maybe provided for each pixel. In an example implementation, the depthvalues for each tile may be down-sampled to obtain a subset ofdown-sampled depth values for the frame, including one or more depthvalues per tile. Also, according to an example embodiment, a frame maybe divided into a plurality of polygons (e.g., rectangles, triangles),where a down-sampled depth value may be determined for each vertex ofone or more of the polygons for the frame. For example, a coordinateposition may be determined for the vertex. Then, the EDS device maydetermine, from the subset of down-sampled depth values, a down-sampleddepth value that has a same (or overlapping) coordinate location as thevertex to be the down-sampled depth value for the vertex.

As noted, only a subset of down-sampled depth values are provided ordetermined for a frame, e.g., for each tile of the frame. One (or more)of these down-sampled depth values may be assigned to or determined foreach vertex. According to an example implementation, rather thanprocessing a separate depth value for each and every pixel of a frame toperform time-warping, a system may process the subset of down-sampleddepth values, e.g., a depth value at/for each vertex, to perform a depthvalue adjusted time-warping of the frame. In this manner, a moreeffective and efficient depth-adjusted time-warping may be performed,e.g., which may reduce the computational load for such time-warping. AnEDS device may then perform, based on at least the adjusted position ofthe vertex, a depth-adjusted time-warping of a frame. According to anexample embodiment, an adjusted position (e.g., x′, y′) for a vertex maybe determined based on a change in a user's head pose and thedown-sampled depth value for (or at) the vertex. For example, anadjusted position may be determined for each vertex of a plurality (orgroup) of vertexes of a polygon. According to an example embodiment, inorder to perform a depth-adjusted time-warping on the frame, anelectronic display stabilization (EDS) device (for example) may, foreach of one or more polygons of the frame, determine an adjustedposition for one or more pixels within the polygon by interpolatingbetween adjusted positions of a group of vertexes of the polygon.

Therefore, according to an example embodiment, a technique may includedetermining a depth value for each of a plurality of pixels of a frame,down-sampling the depth values of a tile of the frame to obtain aplurality of down-sampled depth values, the frame including one or moretiles, determining a change in a head pose, determining, from theplurality of down-sampled depth values, a down-sampled depth value for avertex, determining an adjusted position for the vertex based on thechange in head pose and the down-sampled depth value for the vertex,performing, based on at least the adjusted position for the vertex, adepth-adjusted time-warping of the frame to obtain a depth-adjustedtime-warped frame, and triggering display of the depth-adjustedtime-warped frame.

In the example embodiment shown in FIG. 1, a user may wear ahead-mounted audio visual device, such as, for example, a head mounteddisplay (HMD) 100. As shown in FIG. 1, the user wearing HMD 100 isholding a portable, or handheld, electronic device 102, such as, forexample, a smartphone, or other portable handheld electronic device (orelectronic handheld controller) that may be paired with, or operablycoupled with, and communicate with, the HMD 100 via, for example, awired connection, or a wireless connection such as, for example, a Wi-Fior Bluetooth connection, or other wireless connection. This pairing, oroperable coupling, may provide for communication and exchange of databetween the handheld electronic device 102 and the HMD 100, so that thehandheld electronic device 102 may function as a controller (e.g.,handheld controller) in communication with the HMD 100 for interactingin the immersive virtual world experience generated by the HMD 100. Inthe example shown in FIG. 1, the user is holding the handheld electronicdevice 102 with his right hand. However, the user may also hold thehandheld electronic device 102 in his left hand, or in both his lefthand and his right hand, and still interact with the immersive virtualworld experience generated by the HMD 100. As noted, the user wears theHMD 100 (as an example of a head-mounted audio visual device) and may beholding (and possibly operating) the handheld electronic device 102.Thus, when the user moves, e.g., changes location or orientation withinthe physical space, the HMD 100 (and possibly the handheld electronicdevice 102) will also change locations and/or orientations within thephysical space, based on the movement of the user.

FIGS. 2A and 2B are perspective views of an example HMD, such as, forexample, the HMD 100 worn by the user in FIG. 1, to generate animmersive virtual experience. The HMD 100 may include a housing 110coupled, for example, rotatably coupled and/or removably attachable, toa frame 120. An audio output device 130 including, for example, speakersmounted in headphones, may also be coupled to the frame 120. In FIG. 2B,a front face 110 a of the housing 110 is rotated away from a baseportion 110 b of the housing 110 so that some of the components receivedin the housing 110 are visible. A display 140 may be mounted on thefront face 110 a of the housing 110. Lenses 150 may be mounted in thehousing 110, between the user's eyes and the display 140 when the frontface 110 a is in the closed position against the base portion 110 b ofthe housing 110. A position of the lenses 150 may be may be aligned withrespective optical axes of the user's eyes to provide a relatively widefield of view and relatively short focal length. In some embodiments,the HMD 100 may include a sensing system 160 including various sensorsand a control system 170 including a processor 190 and various controlsystem devices to facilitate operation of the HMD 100.

In some embodiments, the HMD 100 may include a camera 180 to capturestill and moving images of the real world environment outside of the HMD100. In some embodiments the images captured by the camera 180 may bedisplayed to the user on the display 140 in a pass through mode,allowing the user to temporarily view the real world without removingthe HMD 100 or otherwise changing the configuration of the HMD 100 tomove the housing 110 out of the line of sight of the user.

In some embodiments, the HMD 100 may include an optical tracking device165 to detect and track user eye movement and activity. The opticaltracking device 165 may include, for example, an image sensor 165A tocapture images of the user's eyes, and in some embodiments, a particularportion of the user's eyes, such as, for example, the pupil. In someembodiments, the optical tracking device 165 may include multiple imagesensors 165A positioned to detect and track user eye activity. In someembodiment, the optical tracking device 165 may detect and track opticalgestures such as, for example eyelid movement associated with openingand/or closing of the user's eyes (e.g., closing for a threshold periodof time and then opening, opening for a threshold period of time andthen closing, closing and/or opening in particular pattern). In someembodiments, the optical tracking device 165 may detect and track an eyegaze direction and duration. In some embodiments, the HMD 100 may beconfigured so that the optical activity detected by the optical tracingdevice 165 is processed as a user input to be translated into acorresponding interaction in the immersive virtual world experiencegenerated by the HMD 100.

FIG. 3 is a block diagram of a virtual reality system, in accordancewith an embodiment broadly described herein. The system may include afirst user electronic device 300. In some embodiments, the first userelectronic device 300 may be in communication with a second userelectronic device 302. The first user electronic device 300 may be, forexample an HMD as described above with respect to FIGS. 1, 2A and 2B,generating an immersive virtual immersive experience, and the seconduser electronic device 302 may be, for example, a handheld electronicdevice as described above with respect to FIG. 1, in communication withthe first user electronic device 300 to facilitate user interaction withthe virtual immersive experience generated by the HMD.

The first electronic device 300 may include a sensing system 360 and acontrol system 370, which may be similar to the sensing system 160 andthe control system 170, respectively, shown in FIGS. 2A and 2B. Thesensing system 360 may include numerous different types of sensors,including, for example, a light sensor, an audio sensor, an imagesensor, a distance/proximity sensor, an inertial measurement systemincluding for example and accelerometer and gyroscope, and/or othersensors and/or different combination(s) of sensors. In some embodiments,the light sensor, image sensor and audio sensor may be included in onecomponent, such as, for example, a camera, such as the camera 180 of theHMD 100 shown in FIGS. 2A and 2B. In some embodiments, the sensingsystem 360 may include an image sensor positioned to detect and trackoptical activity of the user, such as, for example, a device similar tothe optical tracking device 165 shown in FIG. 2B. The control system 370may include numerous different types of devices, including, for example,a power/pause control device, audio and video control devices, anoptical control device, a transition control device, and/or other suchdevices and/or different combination(s) of devices. In some embodiments,the sensing system 360 and/or the control system 370 may include more,or fewer, devices, depending on a particular embodiment. The elementsincluded in the sensing system 360 and/or the control system 370 canhave a different physical arrangement (e.g., different physicallocation) within, for example, an HMD other than the HMD 100 shown inFIGS. 2A and 2B.

According to an example implementation, sensing system 360 may detect anamount of rotation of a user's head/HMD 100 or a change in rotation of auser's head/HMD 100. According to an example implementation, an amountof rotational time-warping to be performed for a frame may be determinedbased on a change in rotation of a user's head/HMD 100. Sensing system360 may also detect a location of a user's eyes and/or determine atranslation or change in a location of a user's eyes. For example, achange in a location of a user's eyes may be determined based on (or asa) fixed offset(s) from the location of the HMD 100. Also, oralternatively, sensing system 360 may include an eye tracking device totrack the location or change in location of a user's eyes. According toan example implementation, a change in a location of a user's eyes(e.g., either based on fixed offsets of the HMD location or based ondetected eye location by an eye tracking device) may be used todetermine an amount of positional time-warping to be performed for aframe.

The first electronic device 300 may also include a processor 390 incommunication with the sensing system 360 and the control system 370, amemory 380 accessible by, for example, a module of the control system370, and a communication module 350 providing for communication betweenthe first electronic device 300 and another, external device, such as,for example, the second electronic device 302 paired to the firstelectronic device 300.

The second electronic device 302 may include a communication module 306providing for communication between the second electronic device 302 andanother, external device, such as, for example, the first electronicdevice 300 paired with the second electronic device 302. In addition toproviding for the exchange of, for example, electronic data between thefirst electronic device 300 and the second electronic device 302, insome embodiments, the communication module 306 may also be configured toemit a ray or beam. The second electronic device 302 may include asensing system 304 including, for example, an image sensor and an audiosensor, such as is included in, for example, a camera and microphone, aninertial measurement unit, a touch sensor such as is included in a touchsensitive surface of a handheld electronic device, and other suchsensors and/or different combination(s) of sensors. A processor 309 maybe in communication with the sensing system 304 and a controller 305 ofthe second electronic device 302, the controller 305 having access to amemory 308 and controlling overall operation of the second electronicdevice 302.

According to an example embodiment, in order to improve performance oftime-warping in a VR system without adding significant latency, a subsetof down-sampled depth values may be used to adjust or scale time-warpingfor a frame. As shown in FIG. 3, the first electronic device 300 (whichmay be an HMD) may include a graphics engine (e.g., graphics processingunit/GPU) 414 for performing various graphics operations, such as, forexample, for rendering a frame, and also down-sampling depth values foreach tile of a frame to obtain a subset of down-sampled depth values forthe frame. First electronic display device 300 may also include anelectronic display stabilization (EDS) device 418 for performing adepth-adjusted time-warping of a frame based on a change in a head posefor a user and one or more of the down-sampled depth values of thesubset of down-sampled depth values. Graphics engine 414 and EDS device418 are described in greater detail in FIG. 4 according to an exampleembodiment.

FIG. 4 is a block diagram illustrating a virtual reality (VR) system 400according to an example embodiment. VR system 400 may be (or mayinclude), for example, HMD 100 (FIG. 1) or first electronic device 300(FIG. 3), by way of illustrative example, or other VR system. A virtualreality (VR) application 412 may generate and/or receive (via a network,for example) virtual reality content, including one or more frames. Acolor value and a depth value for each pixel of the frame may bereceived by a graphics engine (GPU) 414 via line 434, for example. Eachdepth value may indicate a relative depth for a pixel of the frame.

VR system 400 may include a sensing system 360 (e.g., which may be thesame as sensing system 360, FIG. 3), e.g., for measuring and/ordetermining a pose of the user's head and/or pose of an HMD. Sensingsystem 360 may include, for example, an inertial measurement unit (IMU),accelerometers, optical detectors, cameras or other devices to detect orsense a pose (e.g., location and/or orientation) of the user's head orof an HMD 100, including an initial pose used by graphics engine 414 torender a frame, and an updated pose of the user's head/HMD 100 that maybe used to perform time-warping of the frame. VR system 400 may includeone or more graphics engines, such as graphics engine 414 (which may bea graphics processing unit/GPU), for rendering one or more frames of thevirtual-reality content based on an initial head pose information for auser's head/HMD 100, for example. Graphics engine 414 may receive headpose information, at different points in time, from sensing system 360.

As noted, in some cases, while a graphics engine 414 or GPU is renderinga frame, a user's head/HMD 100 may move, causing the pose (e.g.,location/orientation) information for the user's head/HMD 100 to changeor be inaccurate by the time the frame is output to the display 430.

Therefore, according to an example embodiment, in order to compensatefor the rotation and/or translation (e.g., change in location orposition) of the user's head/HMD 100, an electronic displaystabilization (EDS) engine 418 may perform time-warping on a frame(s)received from graphics engine 414 based on an updated head poseinformation (or based on a change in head pose information) receivedfrom sensing system 360. In order to improve time-warping performance,EDS device 418 may perform depth-adjusted time-warping of the receivedframe, wherein at least a portion of the time-warping for the frame isadjusted based on one or more depth values of a subset of down-sampleddepth values for the frame. The depth-adjusted time-warped frame 438 isthen provided to scanout block 428, where the frame is then output, orscanned out, to a display device 430 for display to the user. Forexample, EDS device 418 may trigger (or cause) display of thedepth-adjusted time-warped frame upon generating the depth-adjustedtime-warped frame 438.

FIG. 5 is a diagram illustrating a frame vertex grid performingdepth-adjusted time-warping according to an example embodiment.According to an example embodiment, the color values and depth valuesfor a frame may be initially stored in a local memory (or GPU memory)for processing by the GPU/graphics engine 414. At least in some systems,in order to perform time-warping on the frame, the color and depthinformation may be written from local (GPU) memory to main memory sothat time-warping on the frame may be performed by EDS device 418.However, there is typically a very limited bandwidth between the local(GPU) memory and the main memory. Therefore, it may add significantdelay to write a large number of depth values for a frame out to a mainmemory for time-warp processing. Also, due to the limited processingpower of EDS device 418, a significant latency or delay may beintroduced into the time-warp processing at EDS 418 if a depth value foreach pixel is processed to perform (e.g., per pixel) time-warping on theframe.

Therefore, according to an example embodiment, a frame 504, e.g.,including a color value (e.g., R, G, B, alpha values) and a depth valuefor each pixel of the frame, may be received and stored in local (e.g.,GPU) memory. The frame 504 may include a plurality of tiles 506 (orsections). Graphics engine 414 may, for example, down-sample the depthvalues for each tile 506 to obtain one or more down-sampled depth valuesfor each tile. The size of the tile may be determined by VR application412, for example, and may be rectangular, for example, or other shape orsize. For example, as shown in FIG. 5, there may be, as an illustrativeexample, a tile of 256 pixels×256 pixels (256×256), with a depth valueinitially provided for each pixel. By way of illustrative example,graphics engine 414 may down-sample the 256×256 depth values to obtain asubset of down-sampled depth values. For example, graphics engine 414may down-sample the 256×256 depth values to obtain 128×128 depth values,and then, after another down-sampling obtain 64×64 down-samples, untileventually there may be, e.g., 4×4 (e.g., 16) down-sampled depth valuesfor each tile. Other techniques may be used as well to performdown-sampling. For example, The sizes of 256×256 (tile size), and 4×4(size of a set of down-sampled depth values for each tile of a frame)are merely used as illustrative examples, and any sizes may be used.There are various ways in which down-sampling may be performed. Forexample, to down-sample 4 depth values (associated with 4 differentpixels), the 4 depth values may be averaged to obtain one down-sampleddepth value, by way of example. Alternatively, rather than averaging thedepth values, a minimum depth value or a maximum depth value of a groupof depth values may be selected to obtain a down-sampled depth value.After the subset of down-sampled depth values have been determined bygraphics engine 414 and then written from local (GPU) memory to mainmemory, EDS device 418 may then perform depth-adjusted time-warping onthe frame based on one or more of these down-sampled depth values. Byusing a subset of depth values from a frame, an effective depth-adjustedtime-warping of a frame may be performed for a VR system, e.g., whiledecreasing or at least limiting the processing overhead and latencyintroduced due to processing of depth values for the time-warping of theframe.

Also, according to an example embodiment, a frame may be divided into aplurality of polygons (e.g., rectangles, triangles). For example, agraphics engine 414 may render each polygon of a frame (e.g., the framerendered by polygon). For example, when rendering a tile, graphicsengine 414 may render all polygons/triangles that intersect the tile. Aframe vertex grid 510, as an example, may include a plurality ofpolygons and a plurality of vertexes. Locations of the vertexes may bedetermined by VR application 412, and may define triangles to berendered by the graphics engine 414. The frame vertex grid 510 may alsobe provided for performing time-warping of a frame based on down-sampleddepth values. The frame vertex grid 510 may represent a frame or aportion of a frame, e.g., with coordinates or locations shown for eachpolygon and vertex. In this example, the polygons are shown astriangles, but other types of polygons may be used.

In an example implementation, the depth values for each tile may bedown-sampled to obtain a subset of down-sampled depth values for theframe, including one or more depth values per tile. Also, according toan example embodiment, a frame may be divided into a plurality ofpolygons (e.g., rectangles, triangles), where a down-sampled depth valuemay be determined for each vertex of one or more of the polygons for theframe. For example, a coordinate position (e.g., x, y coordinate) may bedetermined for the vertex. Then, the EDS device 418 may determine (orselect), from the subset of down-sampled depth values, a down-sampleddepth value that has a same (or overlapping, or nearest) coordinatelocation as the vertex, or based on interpolation of multiple nearbydepth values (that are near the vertex).

As noted, only a subset of down-sampled depth values are provided ordetermined for a frame, e.g., for each tile of the frame, and then usedfor time-warping. One (or more) of these down-sampled depth values maybe assigned to or determined for each vertex. According to an exampleimplementation, rather than processing a separate depth value for eachand every pixel of a frame to perform time-warping, VR system 400 mayprocess the subset of down-sampled depth values, e.g., a depth valueat/for each vertex, to perform a depth-adjusted time-warping of theframe. In this manner, a more effective and efficient depth-adjustedtime-warping may be performed, e.g., which may reduce the computationalload for such time-warping.

EDS 418 may determine an adjusted position for a vertex based on achange in head pose and a down-sampled depth value for the vertex. EDSdevice 418 may perform, based on at least an adjusted position of thevertex, a depth-adjusted time-warping of a frame, e.g., which mayinclude, by way of illustrative example: using interpolation todetermine adjusted positions of one or more pixels within a polygon.

According to an example embodiment, an adjusted position (e.g., x′, y′)for a vertex may be determined based on a change in a user's head poseand the down-sampled depth value for (or at) the vertex (or at the x,ycoordinate of the vertex). For example, an adjusted position may bedetermined for a vertex, or for each vertex of a plurality (or group) ofvertexes of a polygon. According to an example embodiment, in order toperform a depth-adjusted time-warping on the frame, an electronicdisplay stabilization (EDS) device 418 may, for each of one or morepolygons of the frame, determine an adjusted position for one or morepixels within the polygon by interpolating between adjusted positions ofa group of vertexes of the polygon.

By way of illustrative example, referring again to the frame vertex grid510 in FIG. 5, each triangle may include three vertexes (or vertices).For example, triangle 511 may include vertexes 512, 514 and 516. Avertex may be an intersection of two lines or sides of thepolygon/triangle. The vertexes of a triangle define the triangle, forexample. For example, graphics engine 414 may determine a down-sampleddepth value A for vertex 512, a down-sampled depth value B for vertex514, and a down-sampled depth value C for vertex 516, where A, B and Cmay, for example, be numbers or values indicating a depth or relativedepth at or for the vertex. Each down-sampled depth value for a vertexmay, for example, be a down-sampled depth value from one of the tiles506. For example, a down-sample depth value may be selected ordetermined for a vertex where: the (e.g., x, y) coordinates or locationof the down-sampled depth value within the tile or frame 504 matches (ormost closely matches) or corresponds to or overlaps the location orcoordinates of the vertex within the frame vertex grid 510.Alternatively, a depth value for a vertex may be calculated as anaverage or interpolation of two or more down-sampled depth values of aframe or tile.

The frame vertex grid 510 may, for example, reflect (or may be) the sizeand/or resolution of a display device (and/or coordinates or locationswithin the display device), and may allow the frame to be divided into aplurality of polygons or triangles. Each polygon or triangle within theframe vertex grid 510 may include a plurality of pixels to be displayedon a display device. Depth adjusted time-warping of the frame (e.g.,including for the pixels of the frame) may include shifting or movingthe position of each pixel of the frame to a new or adjusted positionbased on a change in head pose and depth information for the frame.Rather than using a depth value for each pixel to determine adepth-adjusted position of each pixel, the depth adjusted time-warpingof the frame may be somewhat simplified by using a down-sampled depthvalue for a vertex (or for each of multiple vertexes). For example, adepth-adjusted time-warping of a frame may include: 1) determining anadjusted position (x′, y′) for a vertex (or for an x,y coordinate of thevertex) based on a change in head pose and the down-sampled depth valuefor the vertex/initial x,y frame coordinate of the vertex, and 2)performing (e.g., based on interpolation), based on the adjustedposition (e.g., x′, y′), or based on an x,y offset, for the vertex orfor a plurality of the vertexes, a depth adjusted time-warping of theframe to obtain a depth-adjusted time-warped frame.

According to an example embodiment, a group (of one or more) of vertexesmay be provided for each triangle or polygon. For example, as noted,vertexes 512, 514 and 516 are provided for triangle 511. For example,vertex 516 may be provided at an initial location/position of x,y (e.g.,indicating position in a horizontal and vertical dimensions of thedisplay), and then may be moved or shifted by an offset 524 (dx, dy)such that the vertex 516 is provided at an adjusted position (x′, y′).

According to an example embodiment, performing a depth-adjustedtime-warping on the frame may include the EDS device 418 performing thefollowing for each of one or more polygons/triangles: determiningadjusted positions for pixels within the polygon by interpolatingbetween adjusted positions of each vertex of a group of vertexes of thepolygon. Or, for example, a change in a position for a pixel within apolygon may be determined by interpolating position changes (e.g., dx,dy) of vertexes of the polygon. Thus, computational complexity ofdepth-adjusted time-warping may be decreased (and thereby decreaselatency) by using only a subset of down-sampled depth values todetermine an adjusted position (e.g., adjusted coordinate, x′, y′) foreach vertex based on a change in head pose and the down-sampled depthvalue for the vertex, and then interpolating the adjusted vertexpositions/coordinates of a polygon/triangle to determine adjustedpositions (or adjusted coordinates) of pixels within thepolygon/triangle. In some example embodiments, interpolating betweenvalues can be performed very fast and inexpensively by a GPU/graphicsengine 414 or by EDS device 418.

According to an example embodiment, an adjusted position (e.g., x′, y′)for each of a plurality of vertexes may be determined based on a changein head pose for a user or HMD and the down-sampled depth value for thevertex. For example, an electronic display stabilization (EDS) device418 may determine, based on a transform matrix, an adjusted position(e.g., x′, y′) for each of the plurality of vertexes based on a changein the head pose of the user and an initial position (e.g., x, y) ofeach of the vertexes. The transform matrix and the adjusted position fora vertex may be adjusted based on the down-sampled depth value for thevertex (e.g., where a greater change in position is provided for avertex having a lesser down-sampled depth value, and a lesser change inposition is provided for a vertex having a greater down-sampled depthvalue). According to an example embodiment, the adjusted position for avertex may be based on a position offset for the vertex, which mayinclude a positional time-warp component that is scaled or adjustedbased on a down-sampled depth value for the vertex. In an exampleembodiment, the adjusted position (adjusted x,y frame coordinate) foreach of a plurality of the vertexes (or coordinates of the vertexes) mayinclude an adjusted x, y position (e.g., x′, y′) based on an x, y offset(dx, dy) from an initial x, y position of the vertex.

According to an example implementation, the time-warping may includerotational time-warping due to rotation of a user's head, and positionaltime-warping due to translation (or change in location or position) of auser's head, wherein the positional time-warping is scaled or adjustedbased on a depth value for one or more vertexes.

According to an example embodiment, determining an adjusted position fora vertex may actually mean or include that, for an x,y frame coordinateat the vertex, an adjusted x,y coordinate is determined. Rather than thevertexes changing position, an x,y frame coordinate initially (beforetime-warping) at the vertex may be shifted or adjusted to a new oradjusted x,y frame coordinate (which may be indicated as x′, y′). Thus,according to an example embodiment, the vertexes may be stationarywithin a frame vertex grid 510, but an x,y coordinate/position at thevertex may move or shift by an x,y offset, to an updated or adjusted x,yframe coordinate/position (x′,y′). For example, a frame vertex may beprovided at an x,y frame coordinate. An adjusted (or updated) positionof the x,y coordinate, based on a change in head pose and a down-sampleddepth value at the x,y frame coordinate of the vertex may be determinedas an x,y offset (dx, dy) from the x,y frame coordinate, to obtain anadjusted x,y frame coordinate (x′, y′). Thus, for example, a pixel atthe x,y frame coordinate (of the vertex) may be shifted by dx, dy (x, yoffset) to an adjusted/update x,y frame coordinate, where the x,y offsetfor such pixel initially located at the vertex may be determined basedon a change in head pose and a down-sampled depth value at the x,y framecoordinate of the vertex. Positions of intermediate pixels (pixels notlocated at a vertex) within the polygon may be determined based oninterpolation, for example. Depth-adjusted time-warping may beperformed, where an x,y offset may be determined for each pixel withinthe polygon by interpolating between x,y offsets for the x,y coordinatesof the vertexes of the polygons. The position or x,y frame coordinate ofa pixel within the polygon is then adjusted or shifted by the x,y offsetfor the pixel. Or alternatively, an adjusted x,y frame coordinate foreach pixel within a polygon may be determined by interpolating betweenthe adjusted x,y frame coordinates (or adjusted positions) of the vertexpositions/coordinates.

According to an example embodiment, the vertexes may stay in the sameposition, and the x,y texture (frame) coordinates may be shifted. Thevertex contains the expected (or initial) x,y coordinates into the frame(without time-warping). Then a transformation matrix shifts (by an x, yoffset) the expected x,y coordinates based on the head rotation andposition change. The position translation in the transformation matrixis adjusted based on the depth at that vertex. The result of thetransform is an adjusted texture (frame) coordinate into the sourceframe for the vertex. Once an adjusted frame coordinate is obtained foreach vertex, a texture (or frame) coordinate is then interpolatedbetween the vertexes in the display frame grid 510, e.g., for each pixelwithin a polygon. An x,y offset may be determined for an x,y coordinateon the frame. The result is an adjusted coordinate for (or at) a vertex:x′,y′=x+dx, y+dy (where dx,dy is the offset and x,y is the expectedtexture coordinate at a certain vertex). In an example embodiment, theoffset may be applied by the matrix transform: [x′,y′]=matrix*[x,y],where the position translation and rotation is applied at the same time.The transform performed by the transform matrix is adjusted for eachvertex based on the depth value at (or for) that vertex.

FIG. 6 is a diagram illustrating pixel depth values for a frame or tileaccording to an example embodiment. Different objects (and thusdifferent pixels) within a frame may have a different depth, such as anear depth , a medium depth, and a far depth, such as for a simple casewhere there are 3 example depth values. This is merely a simple example,and many depth values may be provided to distinguish between differentdepths. An application frame 610 may include a plurality of pixels, witha group of pixels 606 that may be provided at a far depth, while a groupof pixels 608 that may be provided at a near (where near depth is closeror lower depth than far depth). An application depth buffer 630 mayindicate a depth value for each pixel, including a depth value of farfor each pixel within region 610, and a depth value of near for allpixels within region 612.

FIG. 7 is a diagram illustrating a down-sampling of pixel depth valuesto obtain a subset of down-sampled depth values for a tile or frameaccording to an example embodiment. An application depth buffer 630 isshown including region 610 that includes pixels with depth values=far,and a region 612 that includes pixels with depth values=near (by way ofillustrative example). Graphics engine 414 may down-sample, per tile, orfor each tile, the pixel depth values from application depth buffer 630,e.g., to obtain a group (e.g., 4×4) down-sampled depth values for thetile or frame. The depth map 710 indicates a depth value for each of the16 down-sampled depth values for the tile or frame, e.g., where there isa 4×4 group of down-sampled depth values. For example, a down-sampleddepth value 730 indicates a depth value=near; a down-sampled depth value732 indicates a depth value=medium distance; and, a down-sampled depthvalue 734 indicates a depth value=far, as an illustrative example.

FIG. 8 is a diagram illustrating a frame vertex grid 810 according to anexample embodiment. According to an example embodiment, frame vertexgrid indicates a vertex at an intersection of a horizontal and verticalline, for a total of 36 vertexes (e.g., with 20 vertexes in the middle,and 20 more vertexes along the border of the frame vertex grid 810).Based on the depth map 710 (FIG. 7), vertex 820 may have a down-sampleddepth value of near; vertex 822 may have a down-sampled depth value ofmedium; and vertex 824 may have a down-sampled depth value of far.

According to an example embodiment, as shown in FIG. 8, each quad orrectangle (or pixels within the quad or rectangle) within the framevertex grid 810 may typically be rasterized as two triangles. Forexample, rasterizing may include a process of rendering a triangle orother geometric primitive to a discrete grid of pixels. One example quador rectangle may be rasterized as the two triangles 808. Differentcoordinates (or coordinate locations or positions) are shown in theframe vertex grid 810, e.g., which may correspond to a coordinate orlocation on a display. For example, the upper left hand corner of theframe vertex grid may correspond to a (x,y) coordinate of (0,0), theupper right hand corner may correspond to a (x,y) coordinate of (1,0),the lower left hand corner may correspond to a (x,y) coordinate of(0,1), and the lower right hand corner may correspond to an (x,y)coordinate of (1,1). For example, to determine a down-sampled depthvalue for a vertex, the EDS device 418 may sample or read thedown-sampled depth value for the coordinate/location of the vertex fromdepth map 710.

The following presents another illustrative example implementation:

-   -   P={x, y, depth}, where P is a pixel, a vertex, or other point of        an image for display, at location {x, y, depth} in image space.    -   Pc=P transformed to camera space (Pc) based on the inverse of        the projection matrix that was used to render the image.    -   Pc′=M*Pc, where M is the head pose change transformation matrix.        Pc′ is time-warped or reprojected location of point or pixel, in        camera space.    -   P′=Pc′ converted from camera space back to image space with the        projection matrix that was used to render the image. P′ is        time-warped or reprojected location of point or pixel, in image        space.

Example 1. FIG. 9 is a flow chart illustrating operation of a virtualreality system according to an example embodiment. The flow chart ofFIG. 9 may be directed to a method of adjusting time-warping of a framefor a virtual reality system based on depth information. Operation 910may include determining a depth value for each of a plurality of pixelsof a frame. Operation 920 includes down-sampling the depth values of atile of the frame to obtain a plurality of down-sampled depth values,the frame including one or more tiles. Operation 930 includesdetermining a change in a head pose. Operation 940 includes determining,from the plurality of down-sampled depth values, a down-sampled depthvalue for a vertex. Operation 950 includes determining an adjustedposition for the vertex based on the change in head pose and thedown-sampled depth value for the vertex. Operation 960 includesperforming, based on at least the adjusted position for the vertex, adepth-adjusted time-warping of the frame to obtain a depth-adjustedtime-warped frame. Operation 970 includes triggering display of thedepth-adjusted time-warped frame.

Example 2. According to an example embodiment of example 1, thedetermining, from the plurality of down-sampled depth values, adown-sampled depth value for a vertex may include: determining acoordinate location of the vertex; and determining, from the pluralityof down-sampled depth values, a down-sampled depth value for thecoordinate location as a down-sampled depth value for the vertex.

Example 3. According to an example embodiment of any of examples 1-2,the determining, from the plurality of down-sampled depth values, adown-sampled depth value for a vertex may include: determining a firstcoordinate location of a first vertex; determining, from the pluralityof down-sampled depth values, a first down-sampled depth value for thefirst coordinate location as a down-sampled depth value for the firstvertex; determining a second coordinate location of a second vertex; anddetermining, from the plurality of down-sampled depth values, a seconddown-sampled depth value for the second coordinate location as adown-sampled depth value for the second vertex; wherein the determiningan adjusted position for the vertex may include: determining an adjustedposition for the first vertex based on the change in head pose and thefirst down-sampled depth value; and determining an adjusted position forthe second vertex based on the change in head pose and the seconddown-sampled depth value.

Example 4. According to an example embodiment of any of examples 1-3,the determining, from the plurality of depth values of the frame, adown-sampled depth value for a vertex may include determining a firstdown-sampled depth value for a first vertex and a second down-sampleddepth value for a second vertex; wherein the determining an adjustedposition for the vertex based on the change in head pose and thedown-sampled depth value for the vertex may include: determining anadjusted position for the first vertex and an adjusted position of thesecond vertex based on the first down-sampled depth value and the seconddown-sampled depth value, respectively; and wherein the performing mayinclude performing, based on at least the adjusted position for thefirst vertex and the adjusted position for the second vertex, adepth-adjusted time-warping of the frame to obtain a depth-adjustedtime-warped frame.

Example 5. According to an example embodiment of any of examples 1-4,the determining a change in a head pose may include: determining aninitial head pose information; rendering the frame based on the colorvalues of the plurality of pixels and the initial head pose information;determining, during or after the rendering, an updated head poseinformation, where a change in head pose is based on a differencebetween the updated head pose information and the initial head poseinformation.

Example 6. According to an example embodiment of any of examples 1-5,down-sampling may include: determining a tile for the frame; anddown-sampling the depth values of the tile to obtain one or moredown-sampled depth values.

Example 7. According to an example embodiment of any of examples 1-6,the time-warping may include rotational time-warping due to rotation ofa user's head, and positional time-warping due to translation or changein location of a user's eyes, wherein the positional time-warping isscaled or adjusted based on a depth value for one or more of thevertexes.

Example 8. According to an example embodiment of any of examples 1-7,the adjusted position for the vertex may be based on a position offsetfor the vertex, the position offset for the vertex including apositional time-warp component that is scaled or adjusted based on thedown-sampled depth value for the vertex.

Example 9. According to an example embodiment of any of examples 1-8,the adjusted position for the vertex may include an adjusted x, yposition based on an x, y offset from an initial x, y position of thevertex.

Example 10. According to an example embodiment of any of examples 1-9,the determining an adjusted position for the vertex may include:determining, based on a transform matrix, the adjusted position for thevertex based on a change in the head pose and an initial position of thevertex, wherein the transform matrix and the adjusted position for thevertex is adjusted based on the down-sampled depth value for the vertex.

Example 11. According to an example embodiment of any of examples 1-10,the vertex includes a first vertex, wherein the first vertex and asecond vertex are provided for a polygon within the frame, wherein anadjusted position is determined for each of the first vertex and thesecond vertex, and wherein the performing a depth-adjusted time-warpingon the frame may include performing the following for the polygon:determining an adjusted positions for one or more pixels within thepolygon by interpolating between an adjusted position of the firstvertex and an adjusted position of the second vertex.

Example 12. According to an example embodiment of any of examples 1-11,wherein the vertex is provided at an x,y frame coordinate, and whereinthe adjusted position for the vertex comprises an adjusted x, y framecoordinate of the vertex based on an x, y offset, wherein the x,y offsetis determined based on a change in head pose and a depth value at thex,y coordinate at the vertex.

Example 13. According to an example embodiment of any of examples 1-12,the vertex may include a first vertex, wherein the first vertex and asecond vertex are provided for a polygon within the frame, wherein thefirst vertex is provided at a first x,y frame coordinate, and wherein anadjusted position for the first vertex may include an first adjusted x,y frame coordinate of the first vertex based on a first x, y offset,wherein the first x,y offset is determined based on a change in headpose and a depth value of the first x,y coordinate; wherein the secondvertex is provided at a second x,y frame coordinate, and wherein anadjusted position for the second vertex may include a second adjusted x,y frame coordinate of the second vertex based on a second x, y offset,wherein the second x,y offset is determined based on a change in headpose and a depth value of the depth x,y coordinate; and wherein theperforming a depth-adjusted time-warping on the frame may includedetermining an x,y offset for one or more pixels within the polygon byinterpolating between the first x,y offset of the first vertex and thesecond x,y offset of the second vertex.

Example 14. According to an example embodiment of any of examples 1-13,the vertex may include a first vertex provided at a first x,y framecoordinate, wherein a second vertex is provided at a second x,y framecoordinate, the first vertex and the second vertex provided for apolygon; wherein an adjusted position for the first vertex may include afirst adjusted x, y frame coordinate of the first vertex based on afirst x, y offset that is determined based on a change in head pose anda depth value at the first x,y coordinate; wherein an adjusted positionfor the second vertex may include a second adjusted x, y framecoordinate of the second vertex based on a second x, y offset that isdetermined based on a change in head pose and a depth value at thesecond x,y coordinate; and wherein the performing a depth-adjustedtime-warping on the frame may include: determining an x,y offset for apixel within the polygon by interpolating between the first x,y offsetof the first vertex and the second x,y offset of the second vertex; andadjusting a position of the pixel within the polygon based on the x,yoffset for the pixel.

Example 15. According to an example embodiment of any of examples 1-14,the vertex may include a first vertex, wherein the first vertex and asecond vertex are provided for a polygon within the frame, wherein anadjusted position is determined for each of the first vertex and thesecond vertex, and wherein the performing a depth-adjusted time-warpingon the frame may include performing the following for the polygon:determining adjusted positions for pixels within the polygon byinterpolating between an adjusted position of the first vertex and anadjusted position of the second vertex.

Example 16. According to an example embodiment of any of examples 1-15,and further including generating, by a head-mounted audio visual device,a virtual world immersive experience within a virtual space; and whereinthe displaying may include: displaying, by the head-mounted audio visualdevice on a display device, the depth-adjusted time-warped frame.

Example 17. According to an example embodiment, an apparatus includes atleast one processor and at least one memory including computerinstructions, when executed by the at least one processor, cause theapparatus to: determine a depth value for each of a plurality of pixelsof a frame, down-sample the depth values of a tile of the frame toobtain a plurality of down-sampled depth values, the frame including oneor more tiles, determine a change in a head pose, determine, from theplurality of down-sampled depth values, a down-sampled depth value for avertex, determine an adjusted position for the vertex based on thechange in head pose and the down-sampled depth value for the vertex,perform, based on at least the adjusted position for the vertex, adepth-adjusted time-warping of the frame to obtain a depth-adjustedtime-warped frame, and trigger display of the depth-adjusted time-warpedframe.

Example 18. According to another example embodiment, a computer programproduct includes a computer-readable storage medium and storingexecutable code that, when executed by at least one data processingapparatus, is configured to cause the at least one data processingapparatus to perform a method including: determining a depth value foreach of a plurality of pixels of a frame, down-sampling the depth valuesof a tile of the frame to obtain a plurality of down-sampled depthvalues, the frame including one or more tiles, determining a change in ahead pose, determining, from the plurality of down-sampled depth values,a down-sampled depth value for a vertex, determining an adjustedposition for the vertex based on the change in head pose and thedown-sampled depth value for the vertex, performing, based on at leastthe adjusted position for the vertex, a depth-adjusted time-warping ofthe frame to obtain a depth-adjusted time-warped frame, and triggeringdisplay of the depth-adjusted time-warped frame.

Example 19. According to an example embodiment, an apparatus includesmeans for performing the method of any of examples 1-16.

Embodiments of the various techniques described herein may beimplemented in digital electronic circuitry, or in computer hardware,firmware, software, or in combinations of them. Embodiments mayimplemented as a computer program product, i.e., a computer programtangibly embodied in an information carrier, e.g., in a machine-readablestorage device (computer-readable medium), for processing by, or tocontrol the operation of, data processing apparatus, e.g., aprogrammable processor, a computer, or multiple computers. Thus, acomputer-readable storage medium can be configured to store instructionsthat when executed cause a processor (e.g., a processor at a hostdevice, a processor at a client device) to perform a process.

A computer program, such as the computer program(s) described above, canbe written in any form of programming language, including compiled orinterpreted languages, and can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program can bedeployed to be processed on one computer or on multiple computers at onesite or distributed across multiple sites and interconnected by acommunication network.

Method steps may be performed by one or more programmable processorsexecuting a computer program to perform functions by operating on inputdata and generating output. Method steps also may be performed by, andan apparatus may be implemented as, special purpose logic circuitry,e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the processing of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. Elements of a computer may include atleast one processor for executing instructions and one or more memorydevices for storing instructions and data. Generally, a computer alsomay include, or be operatively coupled to receive data from or transferdata to, or both, one or more mass storage devices for storing data,e.g., magnetic, magneto-optical disks, or optical disks. Informationcarriers suitable for embodying computer program instructions and datainclude all forms of non-volatile memory, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor andthe memory may be supplemented by, or incorporated in special purposelogic circuitry.

To provide for interaction with a user, embodiments may be implementedon a computer having a display device, e.g., a cathode ray tube (CRT), alight emitting diode (LED), or liquid crystal display (LCD) monitor, fordisplaying information to the user and a keyboard and a pointing device,e.g., a mouse or a trackball, by which the user can provide input to thecomputer. Other kinds of devices can be used to provide for interactionwith a user as well; for example, feedback provided to the user can beany form of sensory feedback, e.g., visual feedback, auditory feedback,or tactile feedback; and input from the user can be received in anyform, including acoustic, speech, or tactile input.

Embodiments may be implemented in a computing system that includes aback-end component, e.g., as a data server, or that includes amiddleware component, e.g., an application server, or that includes afront-end component, e.g., a client computer having a graphical userinterface or a Web browser through which a user can interact with anembodiment, or any combination of such back-end, middleware, orfront-end components. Components may be interconnected by any form ormedium of digital data communication, e.g., a communication network.Examples of communication networks include a local area network (LAN)and a wide area network (WAN), e.g., the Internet.

FIG. 10 shows an example of a generic computer device 1000 and a genericmobile computer device 1050, which may be used with the techniquesdescribed here. Computing device 1000 is intended to represent variousforms of digital computers, such as laptops, desktops, tablets,workstations, personal digital assistants, televisions, servers, bladeservers, mainframes, and other appropriate computing devices. Computingdevice 1050 is intended to represent various forms of mobile devices,such as personal digital assistants, cellular telephones, smart phones,and other similar computing devices. The components shown here, theirconnections and relationships, and their functions, are meant to beexemplary only, and are not meant to limit embodiments of the inventionsdescribed and/or claimed in this document.

Computing device 1000 includes a processor 1002, memory 1004, a storagedevice 1006, a high-speed interface 1008 connecting to memory 1004 andhigh-speed expansion ports 1010, and a low speed interface 1012connecting to low speed bus 1014 and storage device 1006. The processor1002 can be a semiconductor-based processor. The memory 1004 can be asemiconductor-based memory. Each of the components 1002, 1004, 1006,1008, 1010, and 1012, are interconnected using various busses, and maybe mounted on a common motherboard or in other manners as appropriate.The processor 1002 can process instructions for execution within thecomputing device 1000, including instructions stored in the memory 1004or on the storage device 1006 to display graphical information for a GUIon an external input/output device, such as display 1016 coupled to highspeed interface 1008. In other embodiments, multiple processors and/ormultiple buses may be used, as appropriate, along with multiple memoriesand types of memory. Also, multiple computing devices 1000 may beconnected, with each device providing portions of the necessaryoperations (e.g., as a server bank, a group of blade servers, or amulti-processor system).

The memory 1004 stores information within the computing device 1000. Inone embodiment, the memory 1004 is a volatile memory unit or units. Inanother embodiment, the memory 1004 is a non-volatile memory unit orunits. The memory 1004 may also be another form of computer-readablemedium, such as a magnetic or optical disk.

The storage device 1006 is capable of providing mass storage for thecomputing device 1000. In one embodiment, the storage device 1006 may beor contain a computer-readable medium, such as a floppy disk device, ahard disk device, an optical disk device, or a tape device, a flashmemory or other similar solid state memory device, or an array ofdevices, including devices in a storage area network or otherconfigurations. A computer program product can be tangibly embodied inan information carrier. The computer program product may also containinstructions that, when executed, perform one or more methods, such asthose described above. The information carrier is a computer- ormachine-readable medium, such as the memory 1004, the storage device1006, or memory on processor 1002.

The high speed controller 1008 manages bandwidth-intensive operationsfor the computing device 1000, while the low speed controller 1012manages lower bandwidth-intensive operations. Such allocation offunctions is exemplary only. In one embodiment, the high-speedcontroller 1008 is coupled to memory 1004, display 1016 (e.g., through agraphics processor or accelerator), and to high-speed expansion ports1010, which may accept various expansion cards (not shown). In theembodiment, low-speed controller 1012 is coupled to storage device 1006and low-speed expansion port 1014. The low-speed expansion port, whichmay include various communication ports (e.g., USB, Bluetooth, Ethernet,wireless Ethernet) may be coupled to one or more input/output devices,such as a keyboard, a pointing device, a scanner, or a networking devicesuch as a switch or router, e.g., through a network adapter.

The computing device 1000 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as astandard server 1020, or multiple times in a group of such servers. Itmay also be implemented as part of a rack server system 1024. Inaddition, it may be implemented in a personal computer such as a laptopcomputer 1022. Alternatively, components from computing device 1000 maybe combined with other components in a mobile device (not shown), suchas device 1050. Each of such devices may contain one or more ofcomputing device 1000, 1050, and an entire system may be made up ofmultiple computing devices 1000, 1050 communicating with each other.

Computing device 1050 includes a processor 1052, memory 1064, aninput/output device such as a display 1054, a communication interface1066, and a transceiver 1068, among other components. The device 1050may also be provided with a storage device, such as a microdrive orother device, to provide additional storage. Each of the components1050, 1052, 1064, 1054, 1066, and 1068, are interconnected using variousbuses, and several of the components may be mounted on a commonmotherboard or in other manners as appropriate.

The processor 1052 can execute instructions within the computing device1050, including instructions stored in the memory 1064. The processormay be implemented as a chipset of chips that include separate andmultiple analog and digital processors. The processor may provide, forexample, for coordination of the other components of the device 1050,such as control of user interfaces, applications run by device 1050, andwireless communication by device 1050.

Processor 1052 may communicate with a user through control interface1058 and display interface 1056 coupled to a display 1054. The display1054 may be, for example, a TFT LCD (Thin-Film-Transistor Liquid CrystalDisplay) or an OLED (Organic Light Emitting Diode) display, or otherappropriate display technology. The display interface 1056 may compriseappropriate circuitry for driving the display 1054 to present graphicaland other information to a user. The control interface 1058 may receivecommands from a user and convert them for submission to the processor1052. In addition, an external interface 1062 may be provide incommunication with processor 1052, so as to enable near areacommunication of device 1050 with other devices. External interface 1062may provide, for example, for wired communication in some embodiments,or for wireless communication in other embodiments, and multipleinterfaces may also be used.

The memory 1064 stores information within the computing device 1050. Thememory 1064 can be implemented as one or more of a computer-readablemedium or media, a volatile memory unit or units, or a non-volatilememory unit or units. Expansion memory 1074 may also be provided andconnected to device 1050 through expansion interface 1072, which mayinclude, for example, a SIMM (Single In Line Memory Module) cardinterface. Such expansion memory 1074 may provide extra storage spacefor device 1050, or may also store applications or other information fordevice 1050. Specifically, expansion memory 1074 may includeinstructions to carry out or supplement the processes described above,and may include secure information also. Thus, for example, expansionmemory 1074 may be provided as a security module for device 1050, andmay be programmed with instructions that permit secure use of device1050. In addition, secure applications may be provided via the SIMMcards, along with additional information, such as placing identifyinginformation on the SIMM card in a non-hackable manner.

The memory may include, for example, flash memory and/or NVRAM memory,as discussed below. In one embodiment, a computer program product istangibly embodied in an information carrier. The computer programproduct contains instructions that, when executed, perform one or moremethods, such as those described above. The information carrier is acomputer- or machine-readable medium, such as the memory 1064, expansionmemory 1074, or memory on processor 1052, that may be received, forexample, over transceiver 1068 or external interface 1062.

Device 1050 may communicate wirelessly through communication interface1066, which may include digital signal processing circuitry wherenecessary. Communication interface 1066 may provide for communicationsunder various modes or protocols, such as GSM voice calls, SMS, EMS, orMMS messaging, CDMA, TDMA, PDC, WCDMA, CDMA2000, or GPRS, among others.Such communication may occur, for example, through radio-frequencytransceiver 1068. In addition, short-range communication may occur, suchas using a Bluetooth, WiFi, or other such transceiver (not shown). Inaddition, GPS (Global Positioning System) receiver module 1070 mayprovide additional navigation- and location-related wireless data todevice 1050, which may be used as appropriate by applications running ondevice 1050.

Device 1050 may also communicate audibly using audio codec 1060, whichmay receive spoken information from a user and convert it to usabledigital information. Audio codec 1060 may likewise generate audiblesound for a user, such as through a speaker, e.g., in a handset ofdevice 1050. Such sound may include sound from voice telephone calls,may include recorded sound (e.g., voice messages, music files, etc.) andmay also include sound generated by applications operating on device1050.

The computing device 1050 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as acellular telephone 1080. It may also be implemented as part of a smartphone 1082, personal digital assistant, or other similar mobile device.

Various embodiments of the systems and techniques described here can berealized in digital electronic circuitry, integrated circuitry,specially designed ASICs (application specific integrated circuits),computer hardware, firmware, software, and/or combinations thereof.These various embodiments can include embodiment in one or more computerprograms that are executable and/or interpretable on a programmablesystem including at least one programmable processor, which may bespecial or general purpose, coupled to receive data and instructionsfrom, and to transmit data and instructions to, a storage system, atleast one input device, and at least one output device.

These computer programs (also known as programs, software, softwareapplications or code) include machine instructions for a programmableprocessor, and can be implemented in a high-level procedural and/orobject-oriented programming language, and/or in assembly/machinelanguage. As used herein, the terms “machine-readable medium”“computer-readable medium” refers to any computer program product,apparatus and/or device (e.g., magnetic discs, optical disks, memory,Programmable Logic Devices (PLDs)) used to provide machine instructionsand/or data to a programmable processor, including a machine-readablemedium that receives machine instructions as a machine-readable signal.The term “machine-readable signal” refers to any signal used to providemachine instructions and/or data to a programmable processor.

To provide for interaction with a user, the systems and techniquesdescribed here can be implemented on a computer having a display device(e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor)for displaying information to the user and a keyboard and a pointingdevice (e.g., a mouse or a trackball) by which the user can provideinput to the computer. Other kinds of devices can be used to provide forinteraction with a user as well; for example, feedback provided to theuser can be any form of sensory feedback (e.g., visual feedback,auditory feedback, or tactile feedback); and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in acomputing system that includes a back end component (e.g., as a dataserver), or that includes a middleware component (e.g., an applicationserver), or that includes a front end component (e.g., a client computerhaving a graphical user interface or a Web browser through which a usercan interact with an embodiment of the systems and techniques describedhere), or any combination of such back end, middleware, or front endcomponents. The components of the system can be interconnected by anyform or medium of digital data communication (e.g., a communicationnetwork). Examples of communication networks include a local areanetwork (“LAN”), a wide area network (“WAN”), and the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

A number of embodiments have been described. Nevertheless, variousmodifications may be made without departing from the spirit and scope ofembodiments as broadly described herein.

In addition, the logic flows depicted in the figures do not require theparticular order shown, or sequential order, to achieve desirableresults. In addition, other steps may be provided, or steps may beeliminated, from the described flows, and other components may be addedto, or removed from, the described systems. Accordingly, otherembodiments are within the scope of the following claims.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.”

While certain features of the described embodiments have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the scope of theembodiments. It should be understood that they have been presented byway of example only, not limitation, and various changes in form anddetails may be made. Any portion of the apparatus and/or methodsdescribed herein may be combined in any combination, except mutuallyexclusive combinations. The embodiments described herein can includevarious combinations and/or sub-combinations of the functions,components and/or features of the different embodiments described.

What is claimed is:
 1. A method of adjusting time-warping of a frame fora virtual reality system based on depth information, the methodincluding: determining a depth value for each of a plurality of pixelsof a frame; down-sampling the depth values of a tile of the frame toobtain a plurality of down-sampled depth values, the frame including oneor more tiles; determining a change in a head pose; determining, fromthe plurality of down-sampled depth values, a down-sampled depth valuefor a vertex; determining an adjusted position for the vertex based onthe change in head pose and the down-sampled depth value for the vertex;performing, based on at least the adjusted position for the vertex, adepth-adjusted time-warping of the frame to obtain a depth-adjustedtime-warped frame; and triggering display of the depth-adjustedtime-warped frame.
 2. The method of claim 1: wherein the determining,from the plurality of down-sampled depth values, a down-sampled depthvalue for a vertex comprises: determining a coordinate location of thevertex; and determining, from the plurality of down-sampled depthvalues, a down-sampled depth value for the coordinate location as adown-sampled depth value for the vertex.
 3. The method of claim 1:wherein the determining, from the plurality of down-sampled depthvalues, a down-sampled depth value for a vertex comprises: determining afirst coordinate location of a first vertex; determining, from theplurality of down-sampled depth values, a first down-sampled depth valuefor the first coordinate location as a down-sampled depth value for thefirst vertex; determining a second coordinate location of a secondvertex; and determining, from the plurality of down-sampled depthvalues, a second down-sampled depth value for the second coordinatelocation as a down-sampled depth value for the second vertex; whereinthe determining an adjusted position for the vertex comprises:determining an adjusted position for the first vertex based on thechange in head pose and the first down-sampled depth value; anddetermining an adjusted position for the second vertex based on thechange in head pose and the second down-sampled depth value.
 4. Themethod of claim 1: wherein the determining, from the plurality of depthvalues of the frame, a down-sampled depth value for a vertex comprisesdetermining a first down-sampled depth value for a first vertex and asecond down-sampled depth value for a second vertex; wherein thedetermining an adjusted position for the vertex based on the change inhead pose and the down-sampled depth value for the vertex comprises:determining an adjusted position for the first vertex and an adjustedposition of the second vertex based on the first down-sampled depthvalue and the second down-sampled depth value, respectively; and whereinthe performing comprises performing, based on at least the adjustedposition for the first vertex and the adjusted position for the secondvertex, a depth-adjusted time-warping of the frame to obtain adepth-adjusted time-warped frame.
 5. The method of claim 1 wherein thedetermining a change in a head pose comprises: determining an initialhead pose information; rendering the frame based on the color values ofthe plurality of pixels and the initial head pose information;determining, during or after the rendering, an updated head poseinformation, where a change in head pose is based on a differencebetween the updated head pose information and the initial head poseinformation.
 6. The method of claim 1 wherein down-sampling comprises:determining a tile for the frame; and down-sampling the depth values ofthe tile to obtain one or more down-sampled depth values.
 7. The methodof claim 1 wherein the time-warping comprises rotational time-warpingdue to rotation of a user's head, and positional time-warping due totranslation or change in location of a user's eyes, wherein thepositional time-warping is scaled or adjusted based on a depth value forone or more of the vertexes.
 8. The method of claim 1 wherein theadjusted position for the vertex is based on a position offset for thevertex, the position offset for the vertex including a positionaltime-warp component that is scaled or adjusted based on the down-sampleddepth value for the vertex.
 9. The method of claim 1 wherein theadjusted position for the vertex comprises an adjusted x, y positionbased on an x, y offset from an initial x, y position of the vertex. 10.The method of claim 1 wherein the determining an adjusted position forthe vertex comprises: determining, based on a transform matrix, theadjusted position for the vertex based on a change in the head pose andan initial position of the vertex, wherein the transform matrix and theadjusted position for the vertex is adjusted based on the down-sampleddepth value for the vertex.
 11. The method of claim 1, wherein thevertex comprises a first vertex, wherein the first vertex and a secondvertex are provided for a polygon within the frame, wherein an adjustedposition is determined for each of the first vertex and the secondvertex, and wherein the performing a depth-adjusted time-warping on theframe comprises performing the following for the polygon: determiningadjusted positions for pixels within the polygon by interpolatingbetween an adjusted position of the first vertex and an adjustedposition of the second vertex.
 12. The method of claim 1; wherein thevertex is provided at an x,y frame coordinate, and wherein the adjustedposition for the vertex comprises an adjusted x, y frame coordinate ofthe vertex based on an x, y offset, wherein the x,y offset is determinedbased on a change in head pose and a depth value at the x,y coordinateat the vertex.
 13. The method of claim 1, wherein the vertex comprises afirst vertex, wherein the first vertex and a second vertex are providedfor a polygon within the frame, wherein the first vertex is provided ata first x,y frame coordinate, and wherein an adjusted position for thefirst vertex comprises an first adjusted x, y frame coordinate of thefirst vertex based on a first x, y offset, wherein the first x,y offsetis determined based on a change in head pose and a depth value of thefirst x,y coordinate; wherein the second vertex is provided at a secondx,y frame coordinate, and wherein an adjusted position for the secondvertex comprises a second adjusted x, y frame coordinate of the secondvertex based on a second x, y offset, wherein the second x,y offset isdetermined based on a change in head pose and a depth value of the depthx,y coordinate; and wherein the performing a depth-adjusted time-warpingon the frame comprises determining an x,y offset for one or more pixelswithin the polygon by interpolating between the first x,y offset of thefirst vertex and the second x,y offset of the second vertex.
 14. Themethod of claim 1: wherein the vertex comprises a first vertex providedat a first x,y frame coordinate, wherein a second vertex is provided ata second x,y frame coordinate, the first vertex and the second vertexprovided for a polygon; wherein an adjusted position for the firstvertex comprises a first adjusted x, y frame coordinate of the firstvertex based on a first x, y offset that is determined based on a changein head pose and a depth value at the first x,y coordinate; wherein anadjusted position for the second vertex comprises a second adjusted x, yframe coordinate of the second vertex based on a second x, y offset thatis determined based on a change in head pose and a depth value at thesecond x,y coordinate; and wherein the performing a depth-adjustedtime-warping on the frame comprises: determining an x,y offset for apixel within the polygon by interpolating between the first x,y offsetof the first vertex and the second x,y offset of the second vertex; andadjusting a position of the pixel within the polygon based on the x,yoffset for the pixel.
 15. The method of claim 1 wherein the methodfurther comprises: generating, by a head-mounted audio visual device, avirtual world immersive experience within a virtual space; and whereinthe displaying comprises: displaying, by the head-mounted audio visualdevice on a display device, the depth-adjusted time-warped frame.
 16. Anapparatus comprising at least one processor and at least one memoryincluding computer instructions, when executed by the at least oneprocessor, cause the apparatus to: determine a depth value for each of aplurality of pixels of a frame; down-sample the depth values of a tileof the frame to obtain a plurality of down-sampled depth values, theframe including one or more tiles; determine a change in a head pose;determine, from the plurality of down-sampled depth values, adown-sampled depth value for a vertex; determine an adjusted positionfor the vertex based on the change in head pose and the down-sampleddepth value for the vertex; perform, based on at least the adjustedposition for the vertex, a depth-adjusted time-warping of the frame toobtain a depth-adjusted time-warped frame; and trigger display of thedepth-adjusted time-warped frame.
 17. A computer program product, thecomputer program product comprising a computer-readable storage mediumand storing executable code that, when executed by at least one dataprocessing apparatus, is configured to cause the at least one dataprocessing apparatus to perform a method comprising: determining a depthvalue for each of a plurality of pixels of a frame; down-sampling thedepth values of a tile of the frame to obtain a plurality ofdown-sampled depth values, the frame including one or more tiles;determining a change in a head pose; determining, from the plurality ofdown-sampled depth values, a down-sampled depth value for a vertex;determining an adjusted position for the vertex based on the change inhead pose and the down-sampled depth value for the vertex; performing,based on at least the adjusted position for the vertex, a depth-adjustedtime-warping of the frame to obtain a depth-adjusted time-warped frame;and triggering display of the depth-adjusted time-warped frame.